Quick emergancy help needed!

I am just doing an update right now, but it is still doing it when the bar has reached the end, it has done this for 10 miniutes, and i went to look on my usage, and it said it was only 174 mb , but its turning out to be 1gb! ! Please help! I am very worried that it shall drain all my space, or is their a way to cancle an update?

Okay, luckily the iPod has now done the downloading, and has restarted, but now it has just been an aple and a line under neath it, and it has hardly budges for 5 miniutes. Wait, it hasn't even budged...SHOULD I be worried?!?! I am panicing that all my GB's will go! I only had 4.8 before i started, then it went to 4.0! it was supposed to be 174 mb!!!!!!!